Effective obstacle avoidance is necessary in unmanned aerial vehicles. One solution is to apply sonar modules on an unmanned aerial vehicle such as a drone. However, the commonly used sonar module has a directional confinement which relates to a transmitting direction of sound emitted from a sonar emitter. Accordingly, a fully directional obstacle avoidance system would mount at least 4 to 5 sonar modules along directions perpendicular to each other to accomplish effective obstacle detection and avoidance. Yet the sonar module is expensive which makes the unmanned aerial vehicle expensive, which is unsatisfactory for an increased demand. In addition, a number of sonar modules would increase size and weight of the drone, which decreases battery endurance.
What is needed, therefore, is to provide a sonar obstacle avoidance system and method, and unmanned aerial vehicle to solve the above described problems.